1. Field of the Invention
The invention concerns an electricity meter having a basic meter which requires calibration.
2. Description of the Prior Art
DE 196 05 653 discloses a digital electricity meter to which signals from a consumer or a load can be fed by way of sensors for current and voltage. The detected signals are digitized by means of an A/D-converter and fed to a digital processing device. There, the most widely varying computation procedures, in particular the computation of energy or meter values, are then executed by means of various modules which are substantially in the form of software units. The most widely varying computation operations are possible for that purpose. Output or signaling of the items of information ascertained is then implemented by way of a display and/or an optical or an electrical interface. The interface, the display and a keyboard for the input of information are activated by way of a control device.
For accounting purposes an electricity meter of that kind must meet a calibration requirement and therefore has to be certified. For that purpose the casing or a region which is not accessible to the user, for example a space which can be closed by a flap, can usually be secured by a lead seal so that intervention in the meter and in particular in the measuring assembly thereof is thus made more difficult and can be monitored.
However there is often a need on the part of the users to expand or modify functions on the meter. That however is generally not possible without intervention in the meter, whereby the certification lapses. An exception is represented under some circumstances by modular meters which can be expanded with hardware modules without damaging the calibration seal. A meter with an additional module is known for example from DE 197 12 239 C1. The additional module in that case can also be provided with a lead seal. The reference book xe2x80x9cElectrische Energie elektronisch gemessenxe2x80x9d, Dr.-Ing.Martin Kahmann, vde-Verlag GmbH, 1994, pages 154 through 158, also describes modularity in relation to meters.
The object of the present invention is to provide an electricity meter in which simple user-specific functional expansion is afforded without influencing its part which requires calibration.
In accordance with the invention, there is provided an electricity meter having a basic meter which requires calibration, including:
a current sensor and a voltage sensor for detecting signals which represent the energy consumption at an electrical load,
an analog/digital converter device connected downstream of the sensors, and
a digital processing arrangement with at least one associated memory, a display and/or an input/output module, wherein the digital processing arrangement with a computing module on the basis of the detected signals ascertains the energy consumption at the load and outputs same by way of the display and/or the output module,
wherein:
there is provided an additional computing module which is not subject to the calibration requirement,
wherein the computing module has reaction-free access to the signal and/or energy values ascertained and/or stored in the processing arrangement, and
parameters calculated by the computing module can be outputted by way of the display and/or the input/output module and/or an additional output module.
The additional computing module may be used to implement computing operations in user-specific fashion on the basis of detected current and voltage values. That, as it were, provides an additional virtual meter within the meter. It is possible to make the functions which are accessible to the user, in particular a computing function, reaction-free in relation to the xe2x80x9cbasic meterxe2x80x9d, the so-called measuring arrangement, or the main functions of the meter.
That takes account of the needs of users to provide for additional functions or expansions without expansion of the electricity meter in terms of hardware or software. In that case the additional computing module can already be defined in a customer-specific fashion, depending on the respective customer wish, and thereby implemented in the meter, so that the desired functions or computations can be called up immediately.
Optionally, there can also be provided an access module, in particular an editor or an interpreter, so that the desired functions or computations can be defined or modified by the customer. The electricity meter thus becomes xe2x80x9cfreely programmablexe2x80x9dfor predeterminable functions or computations, without official authorization or certification of the actual meter being violated.
The input module advantageously has a multiplier connected upstream thereof, for the production of power values on the basis of the detected current and voltage signals. That reduces the computation expenditure in the processing arrangement, while faster data processing is afforded when the multiplier is in the form of hardware multiplier. The access module can thus also have recourse to the outputted power values.
It is desirable if the digital processing arrangement includes at least one computer. It is alternatively also possible to envisage a dual- or multi-computer arrangement, in which case provision is made for task distribution to the individual computers. Specifically in that case the input/output module and possibly the display and further interfaces and the keyboard can be controlled by a common computer. Depending on the task involved, in the context of the present digital data processing procedures, the computer used can be a microprocessor, a controller and/or a digital signal processor.
Preferably the access module is accessible to a user by way of a keyboard or by way of an interface and an external input unit. For example the meter-specific keyboard can be used as the keyboard. That means that the access module can be operated in a simple manner like a programmable pocket calculator. In regard to access by way of an interface, it is possible for the external input unit to be formed by an external keyboard or also by a PC, terminal or small computer. In that way even complicated computing operations or fimctions can possibly be inputted.
The forms or instructions produced with the access module in the additional computing module can advantageously be stored. That permits permanent recourse to the inputs. In this respect, the storage space provided for that purpose can be made available by a separate memory or can be a part of a memory of the processing arrangement. Storage separation is not absolutely necessary but it can be desirable in individual cases or in relation to specific uses, in particular in regard to freedom from reaction.
The current and voltage sensors are advantageously of a single-phase or three-phase nature so that adaptation to any kinds of mains network is possible. Preferably the basic meter is associated with a region of first access priority and the additional computing module is associated with a region of second access priority. In this respect, the region of first access priority has means for fitting a seal. That means that the electricity meter can be realized in terms of its basic functions in accordance with the requirement for calibration.
The region of second access priority possibly has means for querying an access authorization. In that way this influenceable region can also be protected from manipulation. In the simplest case the querying means can be embodied by a safeguard means, in particular a lead seal. Further possible forms are for example a key or cipher query or a query by way of a keyword by means of the keyboard.